This invention relates to mixing apparatus, and more particularly to a steady bearing for such apparatus. In many installations, where a mixer is mounted on a tank mounting flange with an agitator shaft extending into the interior of a tank or vessel, the contents of which are to be mixed or blended, it is desirable to support the extended end of the impeller shaft within the interior of the tank. Typically, such supports for the extended end of impeller shafts are known as steady bearings or steady bearing supports.
A steady bearing usually has a bearing housing and a support for mounting the bearing housing on an interior tank surface, such as at the bottom of the tank. The bearing housing typically includes a sleeve-type bearing member within which the extended end of the shaft is received and supported. The shaft extended end is usually provided with a wear sleeve which cooperates with the bearing sleeve.
A particular problem exists in the positioning and mounting of such steady bearings within large agitator tanks. It will be appreciated that the agitator shaft, itself, will deviate from the true center of the tank with any slight misalignment or error in the parallelism of the mounting flange, at the top of the tank, in relation to the position of the steady bearing. Further, since it is usually necessary for the steady bearing to be mounted from within the tank, such as by a person descending into the interior of the tank, or be mounted through a bottom access opening in the tank bottom, the exact position of the impeller shaft, after the mixer drive head has been mounted on its mounting flange, cannot always be predicted with great accuracy.
The problem of alignment, both radially and axially, is usually dealt with by shimming the bearing support and/or shimming the mixer head at its mounting flange. This can be a tedious and time consuming task. Often, the installation does not provide sufficient flexibility to achieve proper alignment by shimming alone. This is especially true for bottom supported shafts which exceed 20 feet in length.
There has been a tendency, in industry, simply to force the extended end of the shaft to fit within the steady bearing, such as by causing the shaft to deflect somewhat. Obviously, such deflection is generally undesirable, not only because of the undue wear to which the steady bearing can be subjected, but also due to the flexing within the shaft as it is rotated.
There is accordingly a need for a steady bearing which permits and provides radial positioning through 360 of its center axis, to provide for alignment of the bushing with the actual position of a shaft within a mixing vessel.